Soot pours off a very different type of rocket—in this case, a toy. Black carbon (the main ingredient of soot) is formed from the incomplete combustion of fuel. Image by Flickr user jurvetson.

Soot pours off a very different type of rocket—in this case, a toy. Black carbon (the main ingredient of soot) is formed from the incomplete combustion of fuel. Image by Flickr user jurvetson.

White_Knight_Two_and_SpaceShipTwo_from_directly_below
The SpaceX Dragon approaches the International Space Station in May. Image by NASA.